In the mixing of large bodies of liquid, several different types of mixers have been used, such as water floats and pumps. Generally, the flotation type is not sufficiently controllable in all directions of flow for efficient mixing. Further, pumps and the like are susceptible to clogging and often do not provide sufficient rate of flow for the efficient mixing required in equalization basins, as well as oxidation ditches, sludge holding tanks and other special applications. Mixers are also used in aerated lagoons in which active biological solids are in equilibrium with supplied wastes. The basin is of sufficient depth, normally six to twelve feet, and oxygen is furnished by mechanical aeration to create a turbulence level sufficient to provide adequate liquid mixing. As a result of the mixing, uniform distribution of the wastes and dispersion of the oxygen is achieved and rapid and efficient waste bio-degradation occurs.
Various mixers mounted on masts or upright means are positioned within the body of liquid, as have been developed in recent years, such as the Flygt 4500 submersible mixer and the Air-o-lator hydraulic and electrical mast mounted units. The torque or twisting moment generated by these aerators can be quite substantial and can lead to structural failure of the mast at either the top or bottom mast supports. One means of counteracting this particular problem, as used by competitors, is to extend side braces in an attempt to hold the mast more rigid. However, these side braces, when considering the usual environment of use, tend to become encrusted with sludge and various wastes and garbage materials. In this environment, the less structure extending into the body of liquid, the better. Additionally, the ability to direct the azimuth of liquid flow is generally considered advantageous. The large torque forces from the motors used tends to twist the mast relative to the mount so that these masts become misdirected from the original set azimuth.
The present invention is directed to the bottom stop arrangement for the bracket and motor assembly relative to the mast and an improved upper azimuth lock which tends to set and hold azimuth more tenaciously than did previous structures. Both include vibration dampening materials so as to cause less material fatigue.